Fundamental Parameters Related to Selenium Kα and Kβ Emission X-ray Spectra

We present relativistic ab initio calculations of fundamental parameters for atomic selenium, based on the Multiconfiguration Dirac-Fock method. In detail, fluorescence yields and subshell linewidths, both of K shell, as well as Kβ to Kα intensity ratio are provided, showing overall agreement with previous theoretical calculations and experimental values. Relative intensities were evaluated assuming the same ionization cross-section for the K-shell hole states, leading to a statistical distribution of these initial states. A method for estimating theoretical linewidths of X-ray lines, where the lines are composed by a multiplet of fine-structure levels that are spread in energy, is proposed. This method provides results that are closer to Kα1,2 experimental width values than the usual method, although slightly higher discrepancies occur for the Kβ1,3 lines. This indicates some inaccuracies in the calculation of Auger rates that have a higher contribution for partial linewidths of the subshells involved in the Kβ1,3 profile. Apart from this, the calculated value of Kβ to Kα intensity ratio, which is less sensitive to Auger rates issues, is in excellent agreement with recommended values.

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High Precision Multiple Kev X-Ray Analysis: Tests of Ionization Cross Sections and Monte Carlo Algorithms

Microscopy and Microanalysis ◽

10.1017/s1431927600011326 ◽

1997 ◽

Vol 3 (S2) ◽

pp. 887-888

Author(s):

John T. Armstrong ◽

D. E. Newbury ◽

P. K. Carpenter

Keyword(s):

Monte Carlo ◽

Electron Beam ◽

Cross Section ◽

High Precision ◽

Atomic Number ◽

Ionization Cross Section ◽

Production Rates ◽

Ionization Cross ◽

X Ray ◽

Monte Carlo Algorithms

Determination of the variation of absolute and relative electron-excited x-ray production rates as a function of electron beam energy and sample atomic number is necessary for calculation of the "stopping power" atomic number correction and the relative amount of characteristic fluorescence and for development of “standardless” and Monte Carlo algorithms for quantitative x-ray analysis. Critical to the calculation of x-ray production rates is an accurate expression for the inner shell electron ionization cross section. A large number of expressions have been proposed for the relative x-ray production rates (used in the fluorescence correction)1 and for the ionization cross section used in the atomic number correction, and these yield quite different results. In order to evaluate which expressions gave the most accurate results when applied to quantitative x-ray emission measurements, we performed a series of high precision measurements of x-ray intensities as a function of electron beam accelerating potential for a series of pure element and simple oxide, phosphide, sulfide, and chloride standards for 65 elements ranging in Z from C to U

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Measurement of X-ray Emission Efficiency for K-lines

Microscopy and Microanalysis ◽

10.1017/s1431927604040139 ◽

2004 ◽

Vol 10 (4) ◽

pp. 481-490 ◽

Cited By ~ 14

Author(s):

M. Procop

Keyword(s):

Cross Section ◽

Ionization Cross Section ◽

Detection Efficiency ◽

Ionization Cross ◽

X Ray ◽

Uncertainty In Measurement ◽

Emission Efficiency ◽

Low Emission ◽

Takeoff Angle ◽

First Time

Results for the X-ray emission efficiency (counts per C per sr) of K-lines for selected elements (C, Al, Si, Ti, Cu, Ge) and for the first time also for compounds and alloys (SiC, GaP, AlCu, TiAlC) are presented. An energy dispersive X-ray spectrometer (EDS) of known detection efficiency (counts per photon) has been used to record the spectra at a takeoff angle of 25° determined by the geometry of the secondary electron microscope's specimen chamber. Overall uncertainty in measurement could be reduced to 5 to 10% in dependence on the line intensity and energy. Measured emission efficiencies have been compared with calculated efficiencies based on models applied in standardless analysis. The widespread XPP and PROZA models give somewhat too low emission efficiencies. The best agreement between measured and calculated efficiencies could be achieved by replacing in the modular PROZA96 model the original expression for the ionization cross section by the formula given by Casnati et al. (1982) A discrepancy remains for carbon, probably due to the high overvoltage ratio.

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PIXE MICROANALYSIS OF VERY LOW Z ELEMENTS BY SUB MeV PROTON BEAM

International Journal of PIXE ◽

10.1142/s0129083593000100 ◽

1993 ◽

Vol 03 (02) ◽

pp. 109-120 ◽

Cited By ~ 2

Author(s):

USAMA M. EL-GHAWI

Keyword(s):

Experimental Data ◽

Proton Beam ◽

Cross Section ◽

Ionization Cross Section ◽

Theoretical Calculations ◽

X Rays ◽

Ionization Cross ◽

Ge Detector ◽

Minimum Detection Limits ◽

Modified Theory

Analysis of very low Z elements between Be and Si using sub MeV proton beam is explored based on theoretical calculations and supported by experimental data. With the availability of the new LE Ge detector, Be K α X-rays can be recorded with reasonable efficiency and high resolution. PWBA and the modified theory, ECPSSR, have been used for ionization cross-section calculation. Minimum detection limits (MDL’s) for thin target conditions are presented in the energy range of 150–2500 keV.

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